1. Technical Field
The disclosure relates to a circuit board, and more particularly, to a circuit board and an electronic assembly.
2. Description of Related Art
In the field of electronic assembly, a rigid circuit board (hereinafter referred to as a circuit board) is a common carrier, which is configured to install electronic components (such as a chip package and passive components), so that these electronic components are capable of electrically connecting with each other through the inner circuit of the circuit board. The circuit board is commonly applied to a motherboard or a module board of an electronic device. The circuit board is mainly composed of a plurality of patterned conductive layers and a plurality of dielectric layers alternately stacked to one another. In addition, two patterned conductive layers can be electrically connected through a conductive via. The material of these dielectric layers may include resin.
The afore-described dielectric layer includes a core dielectric layer, which has a thickness several times than thicknesses of other dielectric layers, so as to provide a sufficient structural strength. As such, when a plurality of signal traces and a ground plane that the signal traces refer to are respectively located at two sides of the core dielectric layer, the core dielectric layer having a larger thickness increases the distance between the signal traces and the ground plane, resulting in ineffective reference effect of the ground plane for these signal traces. Thus, the impedance of the signal traces becomes inaccurate. Besides, the cross-talk caused by radiation adjacent to the signal traces may also affect the quality of signal transmission.